Field of Invention
The present invention relates to a machine, and more particular to a drilling and tapping machine, which can stably control a downward movement of a drilling head for precisely drilling a hole with a diameter range of 0.5 to 3 mm.
Description of Related Arts
A drilling and tapping machine generally comprises a drilling head for making a hole on a workpiece through a drilling process or a tapping process. Generally speaking, there are two types of drilling and tapping machine, i.e. are a cantilever type drilling and tapping machine and a desktop type drilling and tapping machine.
Comparing with the cantilever type drilling and tapping machine with the desktop type drilling and tapping machine, the cantilever type drilling and tapping machine provides a bigger working area and an increases the flexibility of operation. In particular, the cantilever type drilling and tapping machine provides a 360° working area to drill a hole on an object or workpiece therewithin. However, the major backward of the cantilever type drilling and tapping machine is that the drilling head thereof can only make a bigger hole through the drilling process and tapping process. In other words, the cantilever type drilling and tapping machine cannot make a hole smaller than 3 mm. In fact, it is impossible for the cantilever type drilling and tapping machine to make a hole with a diameter of 0.5 mm. On the other hand, only the desktop type drilling and tapping machine with very high accuracy configuration can make a hole with 0.5 mm diameter. Accordingly, the high quality desktop type drilling and tapping machine has complicated structural configuration to perform the precise hole drilling operation. The cost, including the operational cost and maintenance cost, of high quality desktop type drilling and tapping machine is expensive. Accordingly, there are two major factors that the cantilever type drilling and tapping machine cannot make such a small hole. The first factor is that during the tapping operation, the powered drilling head must be moved vertically. The drill and tap of the drilling head are forced by a transverse pulling force through other components of the machine in order to ensure the vertical movement of the drilling head. Since the diameters of the drill and tap of the drilling head are relatively small to drill the small hole, the transverse pulling force applied at the drilling head will easily break the drill and tap during the tapping operation. The second factor is that the machine (for both cantilever type drilling and tapping machine and desktop type drilling and tapping machine) must incorporate a retracting device with the drilling head in order to upwardly move back the drilling head to its original position after the tapping operation is completed. The retracting device can be a gas spring or a coil spring to apply a retracting force, i.e. a spring force, to the drilling head. However, the retracting force is relatively large in order to lift up the drilling head. A larger size drill can withdraw such large retracting force when a bigger hole is formed. However, a smaller size drill can be easily broken by the large retracting force or when the drilling head is rapidly lifted up. In other words, if the machine is required for making a small hole, such as 0.5-3 mm, the large retracting force will break the drilling head easily and will damage the threaded portion of the hole as well. Therefore, it is difficult to make a small hole with the conventional machine.
The conventional drilling and tapping machine further comprises a handle for controlling a movement of the drilling head, such that when the handle is actuated, the drilling head is dropped down to drill a hole on a workpiece through a drilling process or a tapping process. For drilling hole with a diameter between 0.5 mm and 3 mm, a screw tap at the drilling head is small in diameter. In other words, a key factor for drilling such small hole is that the drilling head must be dropped down slowly and stably. Therefore, the handle must be actuated to apply the small and stable controllable pressure to the drilling head. As the small and stable controllable pressure applying to the drilling head, the small reaction force will be generated by the screw tap and will be transmitted back to the handle. Therefore, if the pressure is large enough, a large reaction force will be generated, which will break the screw tap instantly. Furthermore, after the drilling hole is formed, the handle must be pulled back to its original position by the returning force, so as to withdraw the screw tap from the drilling hole. If the returning force is too small, the screw tap cannot be pulled upwardly to withdraw from the drilling hole. If the returning force is too large, the screw tap will be broken before the screw tap is withdrawn from the drilling hole. In other words, the returning force cannot be precisely controlled by the operator. The conventional drilling machine generally equips with a gear transmission control to transmit the pivotal movement of the handle to the downward movement of the drilling head. Accordingly, the gear transmission control comprises a rack and pinion structure, such that the pivotal movement of the handle is transmitted to the downward movement of the drilling head via a gear ratio of the rack and pinion structure. However, the major drawback of the rack and pinion structure is that it cannot precisely transmit the small and stable controllable pressure from the handle to the drilling head. In other words, the operator must apply a relatively large actuating force at the handle to actuate the handle. As a result, the pressure applied to the drilling head cannot be precisely controlled. As it is mentioned above, the large reaction force will be generated to break the screw tap by the large pressure at the handle. Therefore, the rack and pinion structure is not suitable for drilling and tapping machine to drill a small drilling hole with a diameter between 0.5 mm and 3 mm. In order to drill the small drilling hole, the conventional drilling and tapping machine must be operated slowly to drop down the drilling head at a very slow speed. The conventional drilling and tapping machine cannot be rapidly shifted between the drilling operation and the tapping operation.
Furthermore, the conventional drilling and tapping machine further comprises base support and a swing arm movably extended from the base support for positioning the drilling head to align with the workpiece. However, there is no locking mechanism to lock up the relative movement between the base support and the swing arm. As a result, during the operation of the drilling head, the vibration of the drilling head will transmit to the base support through the swing arm, such that the drilling head will misaligned with the workpiece by the unwanted movement between the swing arm and the base support.